Problem: Graph this system of equations and solve. $x+y = -4$ $-8x+2y = 2$ $1$ $2$ $3$ $4$ $5$ $6$ $7$ $8$ $9$ $10$ $\llap{-}2$ $\llap{-}3$ $\llap{-}4$ $\llap{-}5$ $\llap{-}6$ $\llap{-}7$ $\llap{-}8$ $\llap{-}9$ $\llap{-}10$ $1$ $2$ $3$ $4$ $5$ $6$ $7$ $8$ $9$ $10$ $\llap{-}2$ $\llap{-}3$ $\llap{-}4$ $\llap{-}5$ $\llap{-}6$ $\llap{-}7$ $\llap{-}8$ $\llap{-}9$ $\llap{-}10$ Click and drag the points to move the lines.
Explanation: Convert the first equation, $x+y = -4$ , to slope-intercept form. $y = - x - 4$ The y-intercept for the first equation is $-4$ , so the first line must pass through the point $(0, -4)$ The slope for the first equation is $-1$ . Remember that the slope tells you rise over run. So in this case for every $1$ position you move down (because it's negative) You must also move $1$ position to the right. $1$ position to the right. $1$ position down from $(0, -4)$ is $(1, -5)$ Graph the blue line so it passes through $(0, -4)$ and $(1, -5)$ Convert the second equation, $-8x+2y = 2$ , to slope-intercept form. $y = 4 x + 1$ The y-intercept for the second equation is $1$ , so the second line must pass through the point $(0, 1)$ The slope for the second equation is $4$ . Remember that the slope tells you rise over run. So in this case for every $4$ positions you move up $1$ position to the right. $4$ positions up from $(0, 1)$ is $(1, 5)$ Graph the green line so it passes through $(0, 1)$ and $(1, 5)$ The solution is the point where the two lines intersect. The lines intersect at $(-1, -3)$.